Abstract:

Considering the characteristics of a large water area and strong evaporation of the plain reservoir in an arid area,Turpan City,Xinjiang,China,the invalid evaporation of the water surface could be restrained by covering the plain reservoir with weighted floating balls having diameters of 100 mm.We studied the monthly evaporation loss from the openings among the floating balls and the wetted surface areas of the weighted floating balls in the wind-wave environment.The research methods used herein are as follows:(1) Evaporation loss from the openings among floating balls:A and B evaporators with an area of 1 m-2 are placed at the top of the dam.The water surface of the A evaporator is covered by floating balls,and the B evaporator is used as a blank control without covering any material.By observing and analyzing the evaporation in these evaporators,we can obtain the evaporation loss rate caused by the openings.(2) Evaporation loss caused by the wetted surface of weighted floating balls in the wind-wave environment:The experiment was conducted  in the reservoir with good wind and open water around.The floating balls were closely arranged in four different area fences (1 m²,2 m²,3 m²,and 4 m²).We observed and analyzed the wetted surface area of the floating balls in the four fences under different wind speeds and calculated the wetting rate of the floating balls in the four fences.The evaporation inhibition rate per unit area of water under the different areas of the weighted floating balls was obtained by combining the two types of evaporation loss rates,and the monthly water-saving efficiency of the weighted floating balls was calculated.Results showed the following:(1) During the non-freezing period from February to November,the evaporation loss rate from the openings among spheres initially increased and then decreased,reaching the highest value of 11.6% in July.During December-January,the evaporation loss rate was 9%,which was the lowest value in the whole year.(2) The water-saving efficiency of the weighted floating balls is the sum of the product of the frequency appearing in each wind speed interval and the evaporation inhibition rate corresponding to each wind speed interval.(3) Under the same coverage area,the wetting rate of the floating balls increased with the increase in wind speed.The larger the coverage area,the slower the wetting rate changed with the wind speed.At the same wind speed,the wetting rate linearly decreased  with the increase in coverage areas.In the same month of the non-freezing period,the water-saving efficiency per unit area increased with the increase in the coverage area.Under each coverage area,the water-saving efficiency per unit area reached the maximum in July at 76.6%,78.1%,79.6%,and 81.2%,and it reached the minimum in April at 51.9%,54.0%,58.2%,and 61.3%.(4) Compared with the ordinary homogeneous floating balls,the weighted floating balls in the windwave environment possess strong antiinterference ability,good stability,and high anti-evaporation and water-saving efficiency.

Key words: plain reservoir in arid area')">

plain reservoir in arid area, weighted floating balls, wetting rate, evaporation inhibition rate, water saving efficiency